The control of flow separation by periodic excitation

We present the application of the new synthetic jet actuator (SJA) to flow separation control over a NACA 0015 wing. The actuator is compact enough to fit in the interior of the wing that has a chord of 0.375 m. The wing was tested in the Texas A&M University Aerospace Engineering 3 ftX4 ft wind tunnel. An experimental investigation into the effects of the synthetic jet actuator on the performance of the wing is described. Emphasis is placed on the capabilities of the actuator to control the separation of the flow over the wing at high angles of attack. The results include force balance measurements, on surface and off surface flow visualization, surface pressure measurements, and wake surveys. All of the reported tests were performed at a free-stream velocity of 35 m/s, corresponding to a Reynolds number of 8.96×10 5 . The angle of attack was varied from -2.0 deg to 29.0 deg.

A New Class of Synthetic Jet Actuators—Part II: Application to Flow Separation Control

The present invention relates to a flow control device and more particularly to reactive modular flow control device with deployable flow effectors. The present invention further relates to a method of operating the flow control device. One embodiment of the present invention includes a method of controlling air flow across a surface of an aircraft under certain flight conditions comprising the steps of sensing fluid separation from the surface by measuring the pressure on the surface; determining a standard deviation of the pressure measurements over a period of time; and deploying a flow of effector in response to the standard deviation of the pressure measurements exceeding a predetermined threshold number.

Flow control device and method of controlling flow

Anovelsubsonicairfoilcirculationaugmenttechniqueusingco-∞owjet(CFJ)toachievesuperioraerodynamicperformanceforsubsonicaircraftisprovednumericallybyCFDsimulation. Theadvantagesofco-∞owjetairfoilincludehighliftathighangleofattack,ultrahigh Cl=Cdat cruise point, and low penalty to the overall cycle e‐ciency of the airframe-propulsion system. Unlike the conventional circulation control (CC) airfoil which is only suitable for landing and taking ofi, the CFJ airfoil can be used for the whole ∞ying mission. No blunt leading and trailing edge is required so that the pressure drag is small. No moving parts are needed and make it easy to be implemented and weight less. The jet to enhance the circulation will be recirculated. Compared with the CC airfoil, the recirculating CFJ airfoil will signiflcantly save fuel consumption because: 1) the power required to energize the jet is less; 2) no penalty to the jet engine thrust and e‐ciency due to the disposed jet mass ∞ow since the jet mass ∞ow is recirculated. For the NACA2415 airfoil studied, at low AOA with moderate momentum jet coe‐cient, the co∞ow jet airfoil will not only signiflcantly enhance the lift, but also dramatically reduce the drag, or even generate the negative drag (thrust). The mechanism is that the co∞ow jet can control the pressure drag by fllling the wake, and could generate negative pressure drag greaterthanthefrictiondrag. Thismayallowtheaircrafttocruisewithveryhighaerodynamic e‐ciency. AthighAOA,boththeliftandthedragaresigniflcantlyhigherthantheairfoilwith no ∞ow control, which may enhance the performance of taking ofi and landing within short distance.

A Novel Airfoil Circulation Augment Flow Control Method Using Co-Flow Jet

Control of dynamic stall using pulsed vortex generator jets

The effects of active separation control on the aerodynamic performance of an advanced fighter aircraft configuration have been determined. Lowspeed wind tunnel tests were performed using a 7% scale lambda-wing model with jet actuators on the wing leading edge flaps. The jets were operated in a pulsed mode and their frequency and amplitude were varied during the experiments. The effects of the jet actuators on the model aerodynamic performance were measured using a six component force balance for several flap configurations and for angles-of-attack (a) up to 40 deg. The results indicate that the pulsed jets are effective in delaying separation and augmenting lift. Maximum increases in lift were approximately 7% and occurred near C,max. Experiments performed to determine the influence of pulse frequency, ff, on control effectiveness showed that control was optimized for nondimensional frequencies, based on freestream velocity, UM, and wing chord, c, near Strc =/p c/Ura= 1. In addition, it was found that control effectiveness increased monotonically with increases in pulse amplitude. When operating the jet actuators on one wing alone, roll moment coefficients of CRoll- 0.011 could be produced. The results of these experiments indicate that leading edge pulsed jet actuators are an effective means of enhancing aerodynamic performance and maneuverability of advanced fighters.

K. McManus

Papers

Airfoil performance enhancement using pulsed jet separation control